Fistula vs Catheter

• Goal is to provide adequate vascular access to meet current kidney replacement therapy requirements without compromising future potential access sites

Decision points for AVF vs catheter

• If dialysis >1 year and patient ≥20 kg, recommendation is for AV fistula whenever possible [PMID 32778223]
  • In patients 10-20 kg, fistulas may still be feasible, but practice will vary by surgeon/institution
• Catheters suitable for:
  • Small patients <10-20 kg
  • Local lack of IR or surgical expertise for fistula placement
  • Poor anatomy (small/obstructed vessels)
  • Anticipate a short time on dialysis

Advantages and disadvantages

• Fistulas have improved long term access survival (patency rate), better
  HD
  adequacy, lower complication rate (fewer procedural interventions, fewer hospitalizations), and do not require foreign body
• Catheters:
  • Can be placed quickly and used immediately
  • Purportedly may improve quality of life (no needles, pain with access), however data do not support this
  • Disadvantages:
    • Frequent malfunctioning (~85-90%) and poor 12 month catheter survival (~30-65%)
    • Presence of central line is single greatest risk factor for bloodstream infection
    • Malposition
    • Thrombosis or stenosis of vein

Actual usage

• Catheter is used in the large majority (>85%) of pediatric patients at
  HD
  initiation. Why?
  • Failure to refer for preemptive placement of AV fistula
  • Ability to use them immediately
    • E.g., if children present acutely with ESKD, have unexpected worsening of underlying CKD, or require transition to
      HD
      because of
      PD
      failure
  • Expected time on dialysis (e.g., days, months, or years) may not be known
• Even in prevalent population, though, AV fistulas used in a minority of patients
  • Often overly optimistic about time on dialysis

When is access determined?

• Modality discussion should be initiated when kidney replacement need is anticipated (e.g., CKD stage 4)
  • Educate patient:
    • Tour dialysis unit
    • Involve child life specialist
    • Explain pros of cons of AV fistula vs central line
    • Consider peer to peer education
  • Discuss planning with vascular access surgeon
    • Multidisciplinary discussion
    • Obtain imaging
    • Discuss maturation plan/timeframe
• Programs should keep an updated list of patients and their potential access needs
• Preemptive AVF should be placed whenever possible (≥3 months before anticipated need)
• Emergency vascular access placement in a known patient should be considered a failure

Catheters

Vessel preference for catheter placement:

• Right IJ > Right EJ > Left IJ > Left EJ > Femoral >>> Subclavian [PMID 16687748, PMID 26751380]

  • In order of lowest complication risk (e.g., malposition, catheter malfunction)
  • Advantages of right sided neck vessels:
    • Superior anatomy: more direct path to SVC, pleural dome is lower on the right, no thoracic duct on the right, vessel is larger diameter on the right in a majority of patients [PMID 16302239]
    • Mechanically the right side is easier for right-handed operators

• Avoid subclavian lines unless absolutely necessary due to very high rates of subclavian stenosis, which restricts the use of AVF in the whole arm due to proximal venous outflow obstruction

  • 30-50% of adult patients will have stenosis of the subclavian after the use of a subclavian line [PMID 3775662]
    • Rates of stenosis would likely be higher (upwards of 80%) in children (smaller veins) and use of
      HD
      catheters (which are large diameter and stiff)
  • Subclavian lines have become less common with wider availability of ultrasound in ICUs

• For catheters with a side access port, the access port (side port) should be at the cavoatrial junction
  • The return port (distal tip) of the catheter should be well within the atrium
  • If the catheter terminates at the cavoatrial junction the side port will suction against the wall of the vena cava
• Tunneled (cuffed) vs untunneled (temporary)
  • Tunneled catheters are preferred if the anticipated duration of dialysis is >14 days
  • Untunneled catheters are more easily displaced and carry higher risk of infection
    • For tunneled catheters, the cuff acts as a barrier between the tunnel and the insertion of the catheter into the vessel
    • Change to tunneled catheter within 2 weeks if anticipating that dialysis will be needed longer
• While a large diameter is ideal for optimizing dialysis flows, also want to avoid occupying the entire vessel lumen, as this can compromise blood flow and increases risk of vessel stenosis

Who places acute dialysis catheters?

• Pediatric IR
• Critical care

Who places chronic dialysis catheters?

• Pediatric IR
• CT surgery after ECMO decannulation
• Transplant surgery
• Hyperammonemia in neonates: general surgery (cutdown)

Tables: catheter selection based on patient size

Best practices

• If possible, preemptive transplantation is preferable to dialysis
• Home
  peritoneal dialysis (PD)
  is preferred over chronic
  hemodialysis (HD)
• Dialysis units should have routine vascular access rounds for ongoing monitoring
• Goal is to provide adequate vascular access to meet current kidney replacement therapy requirements without compromising future potential access sites
  • This requires a multidisciplinary team of surgeons, pediatric nephrologists, and dialysis nurses
  • Surgery team (especially with rotating residents) may need gentle reminders that management of children with ESKD is different than in the adult patients they have experienced with
• Education should be provided to primary care physicians, ED personnel, and anesthesia regarding vessel preservation (e.g., “Save the Vein” campaigns) for any patient who may need dialysis
  • Whenever possible, do not use the big veins on the non-dominant arm for IVs
  • Upper extremity veins are needed for runoff for future fistulae: use of these veins can lead to obstruction, and obstructed veins do not allow adequate flow for fistulas

AV Fistulas

• High flow artery is connected to a low flow vein
  • Fistula: artery and vein are connected directly
  • Graft: a synthetic tube under the skin connects the artery and vein
    • Grafts are almost never used in children, only if all else has failed
• Vein will “arterialize” by developing a thicker wall and be able to tolerate the higher flow after
• May anastomose side of artery to side of vein, or end of vein to side of artery
• If using a deeper vein, the vein may need to be transposed superficially so it can be safely accessed
  • Usually done in stages: the AV fistula is allowed to mature for 4-6 weeks before the vein is transposed
    • Improves AV patency [PMID 20105601]

Impediments

• Biggest impediments: [PMID 24865851]
  • Nurse resistance to accessing fistulas
  • Surgeon resistance
  • Lack of nephrologist referral
• Other impediments:
  • Patient/parent resistance
  • Short expected wait time for transplant (e.g., living donor)
  • Patient age/size
  • Poor/small vasculature

Sites

• Wrist: radial artery + cephalic vein (Bresio-Cimino fistula)
• Forearm: brachial artery + basilic vein
• Antecubital: brachial artery + cephalic vein
• Upper arm/transposed: brachial artery + basilic vein
• Thigh: femoral artery + saphenous vein

Principles

• Vessels are very small in children, which may be challenging to vascular surgeons who work mostly on adults
  • May prompt surgeons to use veins in the upper arms, where the larger vessels meet adult criteria for flow
  • May be a role for plastic or other microvascular surgeons
• AV fistula is the best access for patients who will be on
  hemodialysis
  for over 1 year
  • Beware excessive optimism: time to kidney transplant can be unpredictable and often takes longer than 1 year or even several years
• Definitions:
  • Primary maturation: spontaneous AVF maturation without radiological or surgical intervention
  • Primary patency: time interval from AVF creation until any intervention to maintain or reestablish patency
  • Secondary patency: time interval from AVF creation until failure (including intervening manipulations designed to re-establish functionality)

After AVF is placed

• Monitor AVF maturation
• If no maturation after 6-10 weeks, discuss revision/intervention with transplant surgeon

AVF outcomes

• Good outcomes in young children (≤20 kg) using microvascular techniques [PMID 29209823]
  • Early failure rate of 12.5%
    • Higher than adults, but still considered acceptable as this gives an 87.5% chance of sparing a proximal site
  • Longer time to maturation in younger children (median 18 weeks)
    • Should be referred much earlier
  • Good patency rates

Maximizing AV Fistula Longevity

Monitoring/Assessment

• Recommended that a trained examiner assess the fistula with a physical exam at least monthly

1. Palpable thrill / audible bruit (bruit more sensitive)
   • Continuous is normal
   • If present only during systole, it may indicate the presence of stenosis
2. Pulse
   • Normal pulse is soft, easily compressible (normal is 3-5/10 intensity)
   • Hyperpulsatility suggests presence of outflow stenosis
3. Augmentation test
   • Palm of hand placed on cannulation segment
   • With other hand, totally occlude outflow vein
   • Normal: thrill disappears, pulse increases in intensity
     • If thrill disappears: no significant accessory vein
     • If pulse increases in intensity: reassures against inflow stenosis
4. Arm elevation test
   • Lift arm above shoulder: fistula should collapse
     • Reassures against outflow stenosis
5. Observation
   • Look for network of collateral veins, variability pulsatility, arm swelling, signs of infection

Clinical signs of AVF dysfunction

• Thrombosis
• Prolonged bleeding (e.g., 20 minutes, or significant increase from baseline)
  • Can indicate presence of outflow stenosis
• Difficulty to cannulate or infiltrated access
  • Can indicate presence of inflow stenosis
• Low KT/V or URR (cannot be explained): inflow or outflow stenosis
• High venous pressure (>250 mmHg): outflow stenosis
• Low arterial pressure (≤250 mmHg): inflow stenosis
• Frequent pressure alarms: misplaced needle; inflow or outflow stenosis
• Aneurysms: repetitive decannulation causing aneurysm, or outflow - stenosis
• Arm/face edema: central vein stenosis
• High recirculation rate: inflow or outflow stenosis
• Cannulation difficulty
• Hand ischemia

Cannulation

• Use aseptic technique
• Ensure adequate initial and ongoing cannulation training
• Cannulation complications:
  • Mild infiltration injury
  • Major infiltrations
    • Can lead to hematoma formation, clotting and fistula loss
  • Infections
  • Pain
  • Aneurysms

Surveillance

• Methods:
  • Intra-access blood flow measurement
  • Static venous dialysis pressure (directly measured or derived) by an outlined method
  • Duplex ultrasound
• KDOQI 2019: does not recommend preemptive intervention for stenosis
  • Wait unless there are clinical indications (e.g., stenosis interfering with dialysis efficiency)
• Reduction in thrombosis rate may help decrease economic costs, prolong access survival, decrease need for emergent procedures, decrease catheter use, decrease missed dialysis treatments, decrease hospitalizations